The following research projects are being continued: 1) Ontogenesis of receptive field characteristics of rabbit visual system; 2) Response characteristics of neurons to visual stimulation in cortical areas outside the primary visual system; and 3) Effects of visual deprivation or brain injury on the responses of visual cells showing possible neuronal plasticity in rabbit visual system. The following are some of the studies: 1. The development of receptive field types of single neurons in both the dorsal and ventral nuclei of lateral geniculate body are determined in new born rabbits. 2. Rabbits reared with eyelid sutured for 25 days may show a retardation of the development of asymmetric cell types in the striate cortex. This is in contrast to the lack of any changes of the cells when eyelid was sutured for three months. 3. Cells in a small region of the rabbit temporal cortex respond to visual stimulation with a short latency of about 50 msed. Their receptive fields are large, about 20-40 degrees, and have complex properties. The afferent and efferent connections of this area are studies and whether this area serves some high order integrative function is determined. 4. Complete ablation of both striate corteces affects a rabbit's ability to learn and to remember previously acquired difficult visual discriminations. This suggests that the cells with recptive fields unique to the striate cortex may be critically involved in the rabbit's pattern vision.